The labor ministry is resorting to naming and shaming tactics as it cracks down on "black companies" — business entities that exploit their workers and fail to improve or take corrective measures despite warnings by the government authorities.

On Wednesday, the Health, Labor and Welfare Ministry published on its website a list of 334 companies that received warnings from the ministry over excessive overtime by employees or whose cases were sent to prosecutors for other kinds of labor law violations since last October. The names of such companies had been always made public, but only through regional labor bureaus. Wednesday’s move marks the first time a nationwide list was released through a central government website.

Included in the list are ad giant Dentsu and electronics manufacturer Panasonic Corp., over which the ministry sent papers to prosecutors after it was discovered they made their employees put in excessive and illegal hours of overtime, as well as Japan Post Co., which had failed to report a work-related injury of an employee who hurt his shoulders while delivering packages.